Sulphating process for ores and concentrates



April 27` 1926.

J. B. READ ET AL SULPHATING PROCESS FOR oREs AND GONCENTRATES Filed Nov, 2e. 1919 msj SQ IINWV 990m o* Venn 55N @Ski h t ma. W m 3. m 4W Am n M KIQLO Patented Apr. 27, `1926.

UNITED STATES Parsirr OFFICE.

`SULIEJI:`[A'lI1\l'G PROCESS FOR ORES AND CONCENTRATES.

Application filed November l To dla/#m it may cm/(cra:

Be it known that we, JonN lrrnNs 'Rust and lVlnLviLLn F. (looms-uml, citizens ol the United States, residing at. Ht'. Louis, Mis- 5 souri, and Golden, Jefferson Count-y, lolorado, respectively, have invented certain new and useful Improvements in Sulphating Processes for Orcs and Com-entrates: and we do declare the following to be a full, clear, and exact description of the, invention, such as will enable others skilled in the. art to which it appertains to make and use the same, reference being had to the accompanying drawings, Awhich form a part-of this` specification.

This invention relates to a one-step proc ess for treating ores and concentrates to eouvert them into sulphates, and while it. applies particularly to sulphides, and more especially to complex sulphides of lead and zinc, it also applies to oxidized minerals and to mixtures of sulphides and oxidized minerals.

Throughout the present case, the term r ores7 is intended to cover not' only raw ores but also concentrates, matte, tailings and by-products containing metal or metal compounds in commercial quantities.

The object of this invention is to recover metals from ores. This is accomplished by forming sulphates 'and separating the soluble sulphates from' the insoluble sulphates and other insoluble material by leaching methods,

Heretofore, inattempting to obtain phates from sulphides, the efforts have largely unsuccessful for two reasons; because the temperatures could erly controlled, since the temperature attained by the combustion of the' sulphides, and required for a rapid' and complete de- .composition of the sulphides, was above the temperature best adapted for the formation of nianyof the sulphates; and second, because the sulphurous gases and metallic oxide formed by the roast, and the excess of oxygen introduced with the 'air during roasting were not brought in contact with each other at the propel' temperaturesto form'the desired sulphates,

tore were traveling in, opposite directions. They present one-step process has four imsulbeen portant features: lFirst, the temperature is since'the gas and' 26,'1919. Serial N0. 340,888.

controlled byeausing the ore or concentrate, and the gaseous products 'ot' the roast, to together with the air required for roasting -travel in the same direction,.that is, concurrently. ly this means the larger portion of the desulphidizing action takes place nearer the feed end of the furnace, and the largerportion of thev sulphating action nearer the discharge end of the furnace.. The reactions of desulphidizing and sulphating, however, are overlapping. The high teni perat-ures developed by the combustion of the sulphides and required for a rapid and efficient decomposition of the same are maintained in the desulphidi-ing zone. In this '/.one only those sulphates will form which have decomposition temperatures y'higher than the ten'iperature'of this Y'one. The temperature is `reduced in the sulphating zone by allowing' radiation through the walls ot' the furnace, or by introducing cold gases directly into the gases of the furnace which are too hot, or by cooling the Walls or rabbles of the furnace with cold gases or liquids. In this zone those sulphates con.- tinue to form which have decomposition temperatures higher tian the temperature of this part of the furnace, and also some unchanged sulphides may be decomposed since the temperature may be sutliciently high for that purpose. Second, much sulphurous gas (SO2) is converted to sulphur-ic gas (SO under the catalytic infiuence of oxids, chietlyferric oxid-Fe2O;,. This action takes place most effectively at temperatures between 550 to 750 C. Third, these gases and metallic oxids formed by the roast and the oxygen from the excess of air introduced for the roast-ing are caused by the concurrent movement of materials to come into contact with each other at the most etlicient temperature for the formation of the desired sulphates. Fourth, a basic vferrie sulphate of the type Fe203-2SO3 is formed from the excess sulphur and iron, which, While insoluble in Water, has a positive solvent 4action in the presence of water onsulphides which have escaped desulphidization and on oxids which have escaped sulphating.

The formation of place between 425 especially effective between 47 5 this basic sulphate takes and 650 C., and is and 550 C.

- In the a sulphatrng For the most successful operation of this process, it is necessary to understand the thermal effects which influence the temperatures in each zone of the furnace. In the desulphidizing zone, oxygen unites with the sulphur of the sulphide minerals and forms gases which are principally SO2, and metallic oxids, and liberates a large amount o heat. Oxygen unites also with sulphurous gas (SO2), forming sulpfhuric gas (S03) under the influence of contact with .already oxidized'material, notably ferrifoxid (Fe,- 03) 'Ihis reaction also liberates heat. 'Ihe temperature of the mineral particles is considerably higher than the temperature' of the gases in this` Zone, due,l to thiJ facty that the .chemical reaction which liberates the heat takes place in the particles themselves, and also that there is a decided resistance to heat flow from a solid to a gas.

' zone some heat is evolved by the union of the sulphurous gas and oxy en, and by the union of the sulphuric gas with the metallic oXids. Also in this zone the temperature of the particles is slightly higher than the temperature of the gases. Here, however,` thevtotal heat liberated is much less than in the desulphidizing zone not only because the heats ofH formation of the compounds from their respective constituents are less, but also because not all of the oXids (especially iron) 'formed in the desulphidizing zone are completely converted to sulphates in the sulphating zone.

So long as the materials are properly moved and thetemperatures controlled; it is immaterial what the direction of moveinent is, or what kind of furnace is used. For inup or down,

v is shown by way vnace in which theore,

stance, the furnace may be'horizontal, or one slightly inclined from the horizontal either or a yertical furnace in which ore and gases move down, or a vertical furif very fine, is blown up with the' gases. In the accompanying drawing, aghorizontal furnace of the rotary type, having a slight downward inclination of example.

In applying this invention to a complex lead and zinc sulphide, Athe ore or concentrate, or both, together with air (and fuel if there is not enough sulphide sulphur to give the heat required, and gases containing sulphur if not enough of these would be formed to sulphatethe metals desired) are introduced into the head of the furnace. -The fuel gases can be separated from the mineral charge by the use of a muiefurnace if desirable, although this is not generally necessary. Here most of the desulphidzing is accomplished, and a temperature between 600 C. and 1000" C. is generally maintained. The best temperature will depend somewhat upon the particular ore or 'concentrate treated. In .this zone the lead, zinc, iron and copper sulphides are changed principally to .oxids lSome zinc ferrite may form. Any gold present is changed to or remains as metal, depending upon its original condition, and any silver'present is change to metal or remains as c loride, depending upon its original con\ dition'i The sulphur of the sulphides is liberated principally 'as.SOz.

JBut, as stated above, S()2 is changed by the catalyticfiniiuenceV of ferrie oxid and rtoja lesser extent by other oxids, into S03. This gas in'turn will act as anoxidiiing agent upon undecomposed sulphideswith the formation of oXids and SO2 again. Since sulphides of iron'fare readily koxidized by the oxygen ofi theu air forming ferric oxid and sulphurousgas, the .ferrie oxid becomes quickly available .Imation of sulphuri'c gas (SOS). Basic lead sulphate and silver sulphate may form here if the temperatures are not too high. 4

The converted minerals and gases are 'gradually moved :along together into a cooler intermediate Zone, the rate of travel depending upon the time required to decompose the sulphides'.t In this intermediate zone, sulphides. are still decomposing and more sulphates and SQ, forming." i

f After further travel, the converted minerals come to a third zone, wherein the temperature is maintained within limits for the formation of the sulphates desired.' Here final. traces of sulphides maybe decomposed and more S03 formed. For an efiicicnt separation of lead and Zinc, a temperature of not less' than 380 C. normore than 850 C.' is maintained. In the final discharge .from the furnace,/ther lead will be found as sulhate or basic sul hate; the zinc (including v that which in the to 'zinc ferrite), copper, metallic silver, an( silver-ch1orids,will`be found as sulphates. If 'the temperature conditions lhave been properly maintained, the iron will be found as oxid and also as basic ferric sulphate of the type Fe2D32SO3, as ydescribed below. The metallic gold will be unaffected. But, if the temperature is allowed to drop too low, much normal ferrie sulphate will form and interfere with the later recovery of metallic zinc. If the temperature runs too high, z nc sulphate will not form and the zinc and lead -compounds can not then be separated. nder no circumstance will any silicio acid form at this place, or in the solution in the subsequent treatment of roasted material with water.

The hot gases in this zone may contain any amount of sulphur gasesthat will effect sulphating. For ..1nstance,.the process may -be carried on with great efficiency using roaster or other gases containing less than three percent by `;volume of such sulphur gases, which small amount is that found in' many metallurgical gases. When ferrie oxidfis present in amounts of 2% or greater,

rst zone was converted in-4 as a catalyzer for the forwhen the gases are not passed in excess of theL usual roasting rate, and when temperatures are controlled as above stated, almost one hundred percent of the Sulphurous and sulphuric gases will be absorbed when they are present in the gas being handled in anv amount as low gases leaving pl these may be returned to the as one percent. VVhenthe iurous and sulphuric content, portions'ot head of. the

the products of combustion, including those from. fuel when used, may be carried along through the various zones. These products vof combustion from fuels used do not materially affect the process of sulphation, but, as above indicated, a mulle oyed if advantageous.

The productsfrom the third zone are treated with Water to dissolve the sulphates of zinc, copper and silver. 'lhevsolution is filtered from the insoluble residue and the above metals separated from the solution y any suitable method, for instance, electro,- lysis. 'Ihe insoluble residue containing the normal or basic lead sulphate or both, the ferric oxid or basic ferrie sulphate or both, the metallic gold and any gangue material, can be smelted to recover the values. Any arsenic or antimony impurities in the original ore 'or concentrate would be either driven ofas gas, or left With the residue.

7e have made the valuable discovery that, during the process of sulphating, if the temperature is controlled Within proper limits`380 C. to 600o C. -(or evenup to 650 C.)-basic ferrie sulphate, above mensulphides to tioned, is formed from the excess of sulphur. and iron which are usually present in complex ores. This basic ferrie sulphate is not soluble in Water, but in the presence ot water it has a upon sulphides which may have escaped desulphidization and upon oxids Which may have escaped sulphating. This action cans .a change of all convertible oxids and sulphates. It is best expressed by the following chemical equations, which probably represent 'the reactions as related to zinc: v

thev basic ferrie water?, enters into the rethe furnace are high in suls sulphate, i

action and is responsible for` practically 100% conversionof `'all convertible oxids and sulphides to sulphates, whereby it is possible to obtainine'arl y complete separation of metals whose sulphates are soluble from those whose sulphates are insoluble.v

rom the foregoing it is seen ,that the tween'bOOo C. and 750 C. Second, by

formingbasic ferrie sulphate from the excess of sulphurous and sulphuric gases, this basic compound in the presence of water still further increasing sulphating. VIn treating'A given in the above illustration,'slightly different temperatures may be needed to effect the differential sulphating desired.

Naturally occurring oxids, carbonates and like compounds maybe mixed with sulphides or sulphur and treated in a similar manner. Also, ferrie oxid may be addedto oxidized minerals, and s ulphurous or sulphuric gases or'both added from an independent source. Sulphurous gas or over ferrie oxid sulphuric gas and.- tl dized mineral. In all cases the concurrent movement during sulphating is as essential as where desulphidizing precedes sulphating, because of the importanceiof keelping the mineral particles in contact with t e gases for an appreciable length of time, chemical reaction can beeifected.

1. A process of sulphating the non-ferrous metal content of sulphide ores, which comprises treating the ores continuously, by continuously advancing the ores, roasting different sulphides from those so that*- the ns passed over the oxiores While carrying the temperature of the ores/at least as high as the decomposition of copper sulphate to convert the sulphides of the ores principally into oxids, moving the/'liberated gases in contact with the ores, in the same direction as the ores being treated throughout the process,l and subjecting the oxidized material non-ferrous metal content of the ore.

which comprises treating the ore in one dvaneing the ore, roasting4 the ore in roasted* materials,

the same same direction throughout.

under treatment in the same direction while in contact with each other, then treating the during agitation and in the presence of said gases at a substantially lower temperature than that used in' the i roasting operation, toA convert the oxids of non-ferrous metals formed in the roasting. operation, into sulphates.

3. A process of sulphating ores which comprises roasting sulphide ores containing iron vand at least one of the metals copper, lead and zinc, at a temperature of about 600 C. to 10.00 GO., lowering` the temperature of the roasted ore to a temperature at which CuSO, is stable, and subjecting the roasted prod oxids of sulphur, and

uct lto the action of passing the ore and tl,1e oxids of sulphur 1n direction through the furnace throughout the entire process.

4. A process of sulphating ores containing iron and sulphatizable metal which comprises feeding such ores to and through a furnace, feeding air to and through such furnace, in the same direction therethrough as the ore, maintaining in the desulphidizing zone a temperature substantially above ,the temperature of 'decomposition of at least some of the sulphates of the sulphatizableA metalsin the ore, whereby the ore is roasted and the metals converted largely into oxids, then lowering the temperature of the roasted material and subjecting the cooled material. to the action of gases containing oxids of sulphur, the gases and solids moving in the 5. A process which comprises first submitting ores containing sulphides in the presprocess.

liberated sulphur oxids sulphate, conveyingphide,

ence of air, to a relativel high temperature favorable to rapid and e cient desulphidization, carrying the sulphur oxids and the roasted ores together in the same .direction into a cooler zone maintained at a temperature favorable to efiicient sulphatization of the sulphatizable minerals the movement being concurrent throughout the entire 6. A process which consists in submitting ores containing sulphides, including iron sulto a temperature favorable to rapid and eflicient roasting and to the conversion of the liberated SO2 to S'OQ, carrying the together with the direction while in zone and thence into. and

roastedore in the saine the desulphidizing vthrough a cooler zone in which the temperathe efficient the sulphatizable minerals. ldescribed process which sulphatization ,of -7. The herein comprises subjecting an ore containing sulphides and containing commercial quantities of both zinc and lead, to a desulphidi-' ing roast at a temperature at least as hig as the 'decomposition temperature of zinc the roasting ore and the 'gases liberated in the roasting operation to a the formation of SQ,

favorable for the sul tained below/the decomposing temperature of zinc sulphate and subsequently leaching the product, whereb substantially all ofthe zine is dissolved and substantially all of the lead is left undissolved.

8. A process of sulphating the non-ferrous metals present in ores containing iron sulphide and zinc or copper compounds, which comprises dead-roasting the iron and copper or zinc content ofthe ore, cooling the roasted product somewhat, maintaining the roasted ore at a temperature favorable for from SO2 and O, maintaining the roasted product at aytemperature favorable for the formation of an'- hydrous basic ferrie-sulphate and maintain;-

ing the roasted product at a temperature favorable for-the sulphating of the non-ferrous metals, all while passing the ore and the gases in contact with each other in the same direction throughout the entire process.

9.A process of sulphating the non-ferrous metals present in ores containing iron sulphide 'and zinc "or copper compounds, which comprises dead-roasting the iron and copper or zinc content of the ore, cooling the roasted product somewhat, maintaining the roasted ore at a temperature favorable' for the formation of SO3 from SO2, and O, maintaining the. roasted product at a temperature favorable f orthe formation of anhydrous basic ferrie sulphate and maintaining the roasted product at a temperature hating of the nonferrous metals, all w ile passing the ore and the gases in contact with each other in the same direction throughout the entire process, and subsequently treating the resulting product with water whereby the basic ferrie. sulphate .aids in dissolving any unsulphated copper or\y zinc.

10. A process which comprises first submitting ores containing sulphur mineral in the presence of air to a` relatively high temperature favorable to rapid and `eicient liberation of sulphur oxides, carrying the sulphur oxides and the ores along together in the same direction while in the desulphidizing zone, and passing said sulphur oXids and ores into a cooler zone maintained at a temperature favorable to efficient sulphatization of the ,solphatizable minerals by said liberated sulphur oxides.

11. A process which comprises submitting ores containing sulphur mineral in the presence of air to a temperature which is at least 'as hi'gh" as the decomposition temperature of the sulphates of certain of the nonferrous sulphatizable metals to produce rapid and efficient .liberation of sulphur oxids, carrying the sulphur oXids-and the treated ores along together in the same direction while in the desulphidizing zone and' and maintaining said cooler zone at a temlower temperature zones of the furnace, perature below said decomposition temperacausingl the gases in 'the furnace to travel ture for the formation of said sulphates of throng the furnace in the same direction said certain metals. as the ore material, and maintaining in some 12. A process which comprises submitting Zone of the furnace a temperature low ores containing sulphur mineral in the presenough for reaction of the ferrite .with the ence of air to a temperature to roast con- OXldS 0f sulphur.

siderably the greater portion of the sulphides The process of sulphating zinc s ulof the ores to oxids and produce rapid and phlde or blende which consists in roasting efficient liberation of sulphur oxids with the the material at a temperature of about 900'J 75 simultaneous formation of sulphur trioxide, C., and then subjecting the 'material to the advancing said sulphur'oxids including the action of the roast gases at a temperature sul )hur trioxide and the roasted ores t-o- .decreasing from 800o C. to 400' C. and in get er into a cooler zone, and maintaining the presence of iron oxide, while movin said -cooler zone at a temperature favorable said gases in parallel current withv the mato the formation of sulphates of the metals tcrial, all the while passing o re and gases of said ores. i 'y 13. A process which comprises submitting throughoutthe entiie process substantially ores containing zinc sulphide and iro-n to aS described. a relatively high temperature to produce 18. A continuous process of sulpliatizi'ng 8* zinc ferrite and liberate sulphur oxids with sulphide ore and minerals which comprises the simultaneous formation of sulphur triroasting the ore in the presence of oxygen oxide, continuously 'moving the minerals and at a temperature at least as high as the desulphur trioxide along together into a cooler whereby the minerals are desulphidized ef 90 zone, and maintaining said cooler zone at a iicientlywitli the formation of oxides, fertempeiature favorable to the formation of rites, sulphates and sulphurous oxide, and zinc sulphate from said zinc ferrite and said with the simultaneous formation of catniitting ores containing sulphurinineral'and advancing the ores and gases in the same silver in at least one ofthe forms of metallic direction. i

silver, silver chloride and silver sulphide, to 19. A one-step continuous process of sula relatively high temperature favorable to phatizing sulphide ores and minerals which rapid and etlicient liberation of sulphur oXids comprises roasting the ore in the presence 00 and whereby any silver sulphide present is of oxygen at a temperature at least as high roasted and metallic silver lformed, carrvas the decomposition temperature'of copper able to the formation of silver sulphate dioxides,` ferrites, sulphatcs and sulphurous rect from said metallic silver and silver oxide, and with the simultaneous formation chloride. of catalyzers for the 'efficient conversion of ting ores containing zinc sulphides and iron advancing and gradually cooling the sulphur to a relatively high temperature in the presoxides and roasted ore together and mainence of air, to produce zinc oxid and iron taining a temperature favorable to the oXid and sulphur oxids, allowing the temfurther formation of sulphates and basic perat'ure to rise sufficiently to produce subsulphates, all while agitating and advancing zinc oxid and iron oxid, continuously mov-` throughout the entire process, and subsezinc ferrite and sulphur oxids. ing roasting the minerals at a high tempera- 6. A process of sulphating ores containture in the presence of oxygen while afritatving sulphides of iron and of non-ferrous ing the minerals for the rapid and e cient sulphatizable metal capable of forming. ferdesulphidization ofthe minerals with the r1te,such process comprising roasting the simultaneous formation of metallic oxides said ores while allowing the temperature in and efficient formation of sulphur trioxide e 'roasting operation to rise high enough for relatively high concentration of said to decompose large amounts of the sulphate sulphur trioXide, all while advancing the of said non-ferrous metal if formed, allow-` minerals and liberated gases concurrently,

ing the formation of ferrite during such whereby sulphates will form readily at said 65 operation, progressivelymovingthe ore to high temperature. 130

2i. A process `for sulphaliziug sulphur bearing minerals containing iron, comprising roasting the minerals at a high temperature in the presence of oxygen while agitating the minerals for the rapid and efficient desulphidization of the minerals with the simultaneous formation of metallic oxides and efficient formation of sulphur trioxide for relatively high concentration of said sulphur trioxide, all While advancing the minerals and liberated gases concurrently, whereby sulpliates will form readily at said high temperature, and carrying the treated minerals and the gases into a cooler zone maintained at a temperature favorable to the efficient further formation of sulphates of the' sulphatizable metals.

22. A method of treating sulphide ores,

the step comprising roasting the sulphidesl at a temperature in excess of (SOOo C.,

causing the said ores together With the air required for roasting and the gaseous products of the roast to travel in the same direction through the furnace.

23. In a method of treating sulphide ores, the step comprising causing the said sulphides together with the air required for roasting and the gaseous products of the roast, to travel iu the same direction (hrm-.gh the furnace and at such a temperature as will cause substantial desulphidization of the ore.

24. The method of roasting` sulphides to produce sulphate which comprises causing the said sulphides together with the air required for roasting and the gaseous products of .the roast to travel in the same direction through the furnace, effecting the desulphidizing action largely near the feell end of the furnace and the sulphating action largely near the discharge end of the furnace.

25. The method of desulphidizing ore containing at least one of the metals, copper and zinc, which comprises roasting the same at a temperature above the decomposition point of the sulphates of at least one of the said metals, causing the said ores to: gether with the air required for roasting and the gaseous prod ucts of the roast to travel in the same direction through the furnace.

In testimony whereof We atlix our sig-- natures.

lJOI-IN BURNS READ.

MELVILLE F. COOLBAUGH.. 

